One phrase to describe it: simply enjoyable.
With multiple semi-upgradable weapons that visually change as you boost them up, the game keeps play feeling fresh and consistently exciting. There's quite like watching a baddy get cut in half by a giant scythe, then flipping off a wall and wailing a hundred strikes in about 2.4 seconds to chop up a demon into that many pieces.
Throughout the game, very little changes withing the fighting system, or the gameplay itself. But why fix what's not broken? Ninja Gaiden offers an exciting, highly enjoyable experience that has just that perfect level of addictive potential.
Buy it. Play it. Watch twelve evil ninjas become four times that many body parts before you can blink.
Loved it.